Control system for mechanically-fired boilers



6 Sheetslsheet 1 w @NA J. NAIMAN Filed vOat.. 8, 1920 CONTROL SYSTEM FOR MECHANICALLY FIRED BOILERS Sept. 27, 1927.

sept.' 27, 1921. A J

NAlMAN CONTROL SYSTEM FOR MECHNCALLY FIRED BOILERS Sept. 27 1927.

J. NAIMAN CONTROL SYSTEM FOR MEGHANICALLY FIRED BOILERS Filed dat. s, 1920 G'Sheetsfsheet 3 NNN.

m mh N, N NN.

6 Sheets-Shagl J. NAIMAN v CONTROL SYSTEM FOR MECHANICALLY FIRED BOILERS I Filed oct. a. 1920 Sept. 27, 1927.

Sept. 2 1

7 927 J. NAIMAN CONTROL SYSTEM FOR MECHAHICALLYFIRED BOILERS Fl'ed Oct. 8, 19.?.0

6 Sheets- Sheet 5 www www Sept.' 27. 1927. 1,643,640

J. NAIMAN CONTROL. SYSTEM FOR MEGHANIGALLY FIRED BOILl-:Rs

Fi 1ed Oct. 8, 1920 heets-:Sheet 6 Paten-ted sept. 27, 1927.

- UNITED STATES PATENT OFFICE.

JULIUS NAIMAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO J'. W. DANA, OF KANSAS CITY',

' MISSOURI.

CONTROL SYSTEM FOR MECHANICALLY-FIRED BOITIERS.

My invention relates to control systems for mechanically fired boilers.

The primary object of the invention is to provide an automatic control system for governing the production of steam in accordance with the demand for the same. l

My invention proceeds on the principle that for the developmentl of a given amount of heatl in the furnace of a boiler a certain amount of fuel must be burned. For the combustion of a given amount of fuel a certain corresponding amount of air must be supplied.

According to my invention I propose to control the rate of the feeding of fuel according to the B. t. u. of the steam load. In order to provide the corresponding amount of air I provide means for varying the air supply at the same time and in the psame direction as the variation of the fuel supply. However it is impossible practically to predetermine anyone ratio between rat-e of fuel feed and airyfeed for all conditions of load, fire-box, fuel "bed, etc.

. Therefore, the variation of the air supply With the variation of the fuel supply can give only an approximation of the correct rate of air supply. I vary the air supply at the same time and in the same direction as the variation of fuel supply until the condition of the products of combustion is such as to indicate an incorrect proportion of the fuel and air and lat this point I substitute lautomatically a control of the air supply so as to secure and maintain a proper condition of the products of combustion. In other words, the rough or approximate control of the air supply is secured according to the steam flow, but the final or accurate adjustment is'secured by an accurate analysis ofthe condition of the products of combustion.

In order to maintain the boiler in` proper working condition it is necessary to maintain substantiallyVV a constant level of water therein.- To supply the water taken out in the form of steam, feed-water is injected. The rate at which waterfis taken out in the form of steam is a measure of the r'ate at which feedwater must be supplied to keep the level constant. I therefore govern the rate of feed water injection .according to the reading of the steam meter. However, it is inadvisable to depend solely upon a fixed relation between steam flow and feed water injection for any extended period of time since an errormay be cumulative. I therefore provide a correction or control for the calibration of the feed water control which is governed by the water level in the boiler.

In order to control the supply of fuel air and water according to the steam load as indicated by the steam meter, there are certain requirements which must be met among others being the following.

l. The fuel bed must be maintainedv in proper condition to get uniform effect. That is to say, there must be no noticeable holes in the fire nor clinkers nor any change from the proper thickness of the lire.

2. The properratio of fuel to air must be maintainedto get efficient combustion. According to this requirement it is necessary to increase the fuel feed when the air feed is increased so that there will not be a great excess of air supplied to the fire before there is suiicient fuel to unite with it.

3. The rate of combustion must correspond to the load. Under this requirement it is necessary that the arrangement be sufficiently flexible so that the rate of combustion can be controlled according to the load. j 4. The rate of water feed to the boiler must correspond to the rate of steam going from the boiler. In other words, the feed water in pounds incoming must replace the steam in pounds outgoing in order to maintain a constant level or a constant water content in the boiler.

The automatic apparatus which I provide takesk into account the above factors and such others as are necessary to complete an automatic regulation of the boiler.

,In addition, my invention provides an over-all-eiiiciency meter for indicating the efficiency of the boiler.

While I have referred so far to a single boiler, it is to be understood that a battery of boilers may be controlled under similar circumstances, certain controls being in common and others being individual as I shall describe more in detail.

In the accompanying drawings which form a part of the specication, ll have illustrated diagrammatically one embodiment ot the invention.

The drawing hereto attached is found 'to consist of a single figure covering six sheets marked respectively, part 1 to part 6; part 1 lying when the sheets are properly laid together at the upper lett hand corner; part 2 lying at the upper right-hand corner; part 3 lying below part 1; part 4 lying below part 2; part 5 lying below part 3; and part 6 lying below part 4.

As l have previously indicated, the control and measurement of eiiiciency are intended to be carried on automatically and to this end, the apparatus which l have shown in the drawings comprises mainly the Jfollowing items, the relation ot which l shall describe more in detail.

1. Steam meter.

. Damper control.

. Stoker speed control.

Fuel bed condition indicator. Water feed control.

. Pyrometer.

. Carbon monoxide detector.

. Water level corrector.

. Efliciency meter.

The boiler l which in this case is the first of a battery of two boilers has a suitable water and steam drum 2 below which is provided the bank of water-tubes 3 having a suitable steam nozzle 4 connected to a steam connecting drum 5. The steam header ofr the battery 6 is connected between the drum 5 and the load device to which steam is supplied from one or bot-h of the boilers of the battery.

The boiler 1 is provided with a suitable mechanical stoker in this case consisting of a traveling grate 7 driven by a stoker engine 8,-the speed of which engine is controlled by a. suitable valve 9. Coal is fed from a hopper 11 upon the traveling grate 7 through a delivery chute 12 and a control nozzle 13, which control nozzle governs the thickness of the fuel bed on the grate 7.

The heated products of combustion from the furnace 14 pass up through the water tubes 3 over the first batlle member 15 and thence down through the water tubes under the second'balle 16 and then pass up' through the tubes again and out past the damper 17 to the stack 18-where these gases are eX- hausted. j

The boiler has a suitable feed water 'drum 19 to which is connected the feed water pipe 21 leading from a suitable pumping device such as the steam pump 22.I The control valve 23 which may be automatically controlled as will be described later is connected in the feed water main 21 to govern the rate at which feed water is taken from the hot well 24 and delivered to the boiler. y

The boiler and auxiliary apparatus thus reliance tar described may be of any conventional or suitable type. L shall now describe the steam meter which is a necessary part ot my invention.

(1) Steam meter.

rEhe steam header or main 6 has connected thereto the steam meter body which comprises a U-shaped tube, the ends of which communicate with the interior of the steam header through suitable openings or nozzles `generally called Pitot tubes, whereby the kinetic energy of the steam may be converted to a certain extent in proportion to the rate of flow into a difference in pressure between the t-wo legs ot the U-tube.

It is not essential that this particular form of creating a difference in pressure be einployed, as an orifice, a Venturi-tube or any other suitable means may be employed. rIhe bottom of the U-tube contains a quantityv of mercury. The U-tube in this case comprises an inclined leg 26 along which are arranged contacts 27 for varying a resistance 28. This resistance 28 is connected by means of the leads 29 and 31 into the steam meter circuit which in this case comprises a Wheatstone bridge 32.

The VVheatstone bridge 32 comprises the arms A, B, C and D with the battery circuit 33 and the galvanometer circuit comprising leads 34 and 35 which leads bridge the galvanometer coil 36 of the galvanometer 37 from the common terminal of the arms A and B to the common terminal of the arms C and D. The battery circuit 33 is bridged from the common terminal of the arms A and B to the common terminal of the arms C and D. f

The arm A contains the variable resistance 28 controlled by the rate of flow of steam in the. steam main 6. The arm D'contains the resistance 38 governed by the steam pressure gage 39; the arm C contains constant resistance 41 and the arm B contains the balancing resistance 42 of the steam meter rheostat 43. The resistance 38 is graduated in terms of density or heat content for a purpose 'to be described later.

The steam meter rheostat 43 may be graduated in terms of pounds delivered by the steam or B. t. u. of steam.

I measure the pounds of steam (in the case of wetor saturated steam) by irst measuring the difference in pressure upon the mercury in the U-tube and by measuring the density of thesteam.

' The equation for weight per unit of time in terms of difference in pressure and density is When 7i isthe difference in pressure and D is the density, W is the weight per unit of time, and K is a constant of proportionality. 7

The density is measured by the pressure gauge 39, the rheostat of which is graduated in terms of density since in the case-of a Wet or saturated vapor there is a definite density corresponding to each definite pressure which may be ascertained from 4steam tables.

Thus

(la) D=f(;)

(2) pIKaRa Where p is the difference in l pressure in the U-tuloe, and Ra is the value of the resistance in the arm A and IQ is a constant. Similarly' let Rb, Rc and Rd equal the values of the resistances included in arms B, C and D respectively.

(6) W K@ Kw/IQRa But, when the galvanometer pointer 76 of the VVheatstone bridge 32 is at zero position, the relation between the resistance arms Where K1 K \/K3Kd is a constant.

Ra, Rb, Rc, and Rd is as follows:

RaR (7) Rb= R d Therefore, Equation (6)*may be rewritten, i

or the rheostat 42 whose resistance equals Rb is a measure of the poundsl of steam W flowing per unit of time through the steam header 6.

For the measurement of the B. t. u. of the saturated steam flowing per unit of time, the fact that for any given absolut-e pressure P a certain heat content corresponds to every pound of steam, is utilized. This heat content is a function of the absolute pressure P. Again, the factor 1/D of Equation (l) is also a function of P. Therefore, by multiplying 1/39 by such a combined function of P as to take in w/D as well as the correction for heat content per pound of steam, we get a result which is proportional to the B. t. u. per unit of time of the steam 'stat 38 is calibrated'in terms of F(P) Since the rheostat 38 of the pressure gauge 30 is graduated in terms of density, we have:

DlIKdRd Also, D,L being the density of saturated steam corresponding to the given pressure.

The resistance 41 may be made proportional to the quality v of the steam, and we have (3a) mzKcRc Now, the relation between the density l of saturated steam and the actual density D of the Wet steam of quality fr can be approximately expressed as follows:

Therefore, the relation between D and the resistance Rd can be expressed as follows:

p, KdRd KdRd From the foregoing, the relation between the value of W in pounds of steam per uni-t of time and the resistances ofv thel ste-am meter circuit 32 can evidently be expressed as follows:

KaRd :K RaRd KcRc 1 Rc flowing througn the pipe 6. It is, thus, only necessary to graduate the pressure gauge rheostat 38 in accordance with a certain function of P which is a resultant of the functional relation of P and D and the heat content and P.

Thus-if p where z' is the heat content per pound of steam, then 10 (10) I W'i 12) Jaw/1MP,

15), =K/pF P) 'Vhere I is the total heat content or B. t. u. delivered by the steam per unit of time.-

sity and heat content as previously shown.

Thus,

(16) F(P) :KdRd

Also, as before,

pzKaRa (see 2) and since the B. t. u. per unit of time is expressed by If Re is ixed at some constant value, we have from the Wheatstone bridge circuit 32 RaRd Re Therefore, Equation (17) may be rewritten (19) bmx/l Kn/R-,

(see 15) KgRaRd where is a constant, or the rheostat 42 in this case is a measure of the B. t. u. of steam l flowing per unit of time through the steam header 6.

With such a graduation of rheostat 38 it would still be possible to measure the weight per unit of time by controlling the Value of the resistance 41 in accordance with the absolute temperature of the steam.

The galvanometer 37 controls a relay 44 which is of the type disclosed in U. S. Patent No. 1,376,633 of John A. Obermaier, issued May 3, 1921, which relay controls the rheostat operating motor 45 for operating the rheostat arm 46 to bring the Wheatstone bridge 32 to a condition of balance. The position of the arm 46 is an indication o f the flow of steam in terms of B. t. u. It may when so desired be graduated in terms of pounds.

rllhe rheostat 43 in addition to the resist- .ance 42 has similar variable resistances 47, 48 and 49 which are controlled by the movement of the arm 46, such resistances forming parts of other circuits which require a control in' accordance with the flow of steam. ln practice each rheostat-has its individual control arm electrically independent from. the other circuits, although they are mechanically operated in unison.

The relay 44 comprises two sets of springs, namely, the set 51, 52, 53 for controlling the forward motion of the motor 95 and the sct 54, 55 vand 56 for controlling the reverse motion of the motor 95.

One terminal of battery or other source of current 57 is connected to the interme- Leases@ diate springs 52 and 55, the other terminal of battery being connected by way of the wire 58 to the armature of the motor 95. rlhe forward spring 53 is connected through the low resistance 59 over wire 61 with the forward field winding 62. The other forward spring 51 is connected through the high resistance .63 over the wire 61 which is connected to the forward field 62. Of the reverse springs the contact 54 is connected through high resistance 64 line 65 to the reverse field 66. The other reverse spring 56 is connected through the low resistance 67 to the reverse field 66. A set of plungers is provided for closing the various contacts as desired. these plungers comprising yplungers 68 and 69 for closing contact-s between springs 53 and 52 and springs 52 and 51, respectively. The plungers 71 and 72 close contact between the springs 56-55 and 55-54, respectively. Detent rods lying back of the plungers 68, 69, 71 and 72 are adapted to catch .at the reduced portions of these plungers when the plungers are elevated to hold any plunger which is elevated in position to retain its corresponding contacts closed. A common release bar 73 is adapted to release any of the plungers when it is pushed backward by means of the bell crank lever 74. The coil `36 of the galvanometer 37 has a pointer 75 .which carries a small contact block 76 adapted to lie under any one of the plungers or the end of the bell crank lever 74. A reciprocating platen 77 driven by the cam 78 is adapted to press the block 76 against either the end of the release bell crank 74 or against the ends of the plungers 68, 69, 71 and 72, depending upon the throw of the galvanometer needle .75. The plungers 68 and 69 are provided with a common arm or catch member 7 9 and the plungers 71 and 72 are similarly provided with a common catch arm 81, the purpose of these arms being in each case t0 prevent swinging of the needle past the center point before release of the raised plungers occurs. ln other words, in order to prevent electrical interference, it is necessary that a-plunger on one side be released loe-l fore a plunger is raised on the other side of the central or neutral point. The operation of this relay is to cause actuation of the motor 45 in a forward or reverse direction in order to keep the arm 46 of the steam meter rheostat at a proper value whereby the resistance 42 maintains the steam meter bridge 32 in balance. rlhe manner in which it performs this function will be explained in detail later. The coil 36 is adapted to swing 'either to the right or to the left depending upon whether the resistance 42 should be greater or less to bring the bridge to balance. The result is, if the needle 75 swings to the left as shown in the drawings, the block 76 will lie under plunger 69 or under plunger 68. If the deflection is relatively small it Will lie under plunger 69 so that upon the` next stroke of the reciprocating platen 77 the plunger 69 will be raised and caught by its detent closing a circuit for the motor through the forward field 62 and through the relatively high resistance 63 so that the motor begins to turn in a forward direction to bring the bridge to a balanced cond'ltlon. The motor 45 continues to operate until the bridge is brought to a balanced condition, whereupon, the. pointer or needle 75 of the galvanometer 37 comes back to zero position, whereupon, the next reciprocation of the platen 77 causes the bell crank lever 74 to push back the release plate 7 3 whereby the detent is moved yfrom the plunger 69 and it is restored opening the springs 51 and 5.2. It is to be understood that the platen 77 1s constantly driven at any suitable speed to give short periods of time between posslble opening or closing of the circuit so that a' close regulation may be obtained. Thus the relay with the corresponding motor causes the steam meter rheostat to follow closely and with any desired .degree of accuracy the variations in steam flow through the main 6.

The arms 79 and 81 are adapted to, be lifted by either one of the plungers which each one of these arms serves sothat under no condition can the motor be subjected to both the forward and the reverse field.

In the steam meter Wheatstone bridge 3 2 the steam pressure' gauge resistance 38 1s connected in the arm D over the wires 82, 83 and the balancing resistance 42 is connected in the arm B over the wires 84 and 85.

(2) Damper control.

I shall next describe the damper control for the boiler and the manner in which it is,

effected. It will perhaps clarify the explanation to say that the damper control is affected by the following factors:

1. Steam flow.

2. Stoker speed.

Fire box temperature.

4. Carbon monoxide detector.

5. Fuel bed conditions.

The damper 17 is adapted to be moved by a motor 87 which is shown as connected by a shaft and bevel gearing with the damper `17. It will be understood that the present boiler is shown as having the air supply controlled by the damper 17, the draft being created through a suitable stack or similar device whereby there is what may be termed natural draft. In case forced draft is to be controlled, it will be understood that the same can be effected through the operation of the motor 87 in any suitable manner. Similarlv a combination of forced and natural draft which is commonly termed bal anced draft may be controlled in a manner the casing 45 affects 4similar to that shown in the drawing, with Athe additional regulation of the forced draft or the naturaldraft, as the case may be, by means of a pressure responsive element.

The' motor 87 which operates the dam er 17 is controlled primarily by the stoer speed control relay 121 and also by the draft control relay 88. This latter relay being the electro-responsive element of the damper control bridge 89 which has the four electrical arms E` F, G and H. The battery circuit 91 is bridged across the common points of the arms E and G and arms F and H, while the galvanometer 88 is connected across the common points of the arms E, F and G-H. The arms E and F have thermally controlled resistances 93 and 94 connected therein, respectively, these resistances forming parts of the carbon monoxide detector 92. The carbonl monoxide detector comprises a closed pipe or conduit 45 connecting with the stack or exhaust flue 18 of the boileryat the point 46, the conduit or casing 45 being provided with a small exhaust fan 97 for drawing continuously a sample of the stack gases 'through the opening 46 into the body 45 and out through the fan 97. This sample of gases as it enters n the thermally controlled resistance 93, the gas thenpasses an ignition element, in this case shown as a spark plug 98, where it is ignited and its temperature thereby increased. Thereafter it strikes the thermally.controlled resistance 94. It will be appreclated at once that a difference intemperature between the resistances 93 and 94 w1ll be a measure of the B. t. u. value Aof the stack gases, and hence a measure of the degree of combustion. The carbon monoxide detector thus is able to indicate whether combustion is complete or not, independently of the temperature of the gases which pass out the stack.

The difference in temperature indicated by the difference in resistances 93 and 94 is a measure of the heat developed by the combustion of the CO or any unburned hydrocarbons (correction being made for the 'external heat added by thc ignition element by an additional resistance in series with the resistance 93). Again the heat developed by the combustion of the CO or unburned hydrocarbons is proportional to the equivalent percentage of CO present in the flue gas (by equivalen-t CO is meant the. actual CO plus the amount of CO which when burned would develop the same heat as that developed by the hydrocarbons).

'In other words, the differences between resistances 93 and 94 (assuming that proper1 corrections are made .for external heat added) are a direct measurement of the equivalent percentage of CO in the flue gases.

The thermally controlled resistance 93 is connected over the wires 99 and 101 in the arm E of the damper control bridge 89. rIhe thermally controlled resistance 94 is connected in the arm F overl the wires 102 and 103.

The other arms G and H have connected therein respectively, the pyrometer resistances 104 and 105, respectively, over the wires 106, 107, 108 and 109, respectively. 'Ihese pyrometer resistances 105 and 104 are placed respectively at the intake and the discharge portions of a conduit vthrough which a suitable fluid is constantly discharged. This construction forms a novel arrangement for measuring the temperature of a furnace or the like and is not limited to the particular use to which I have applied the same. It consists of a pipe 111 exposed to the furnace or other source of heat, the temperature of which is to be measured and a constant streamof fluid, preferably water, is caused to flow therethrough. By measuring the temperature of the incoming water, such as I do by means of the resistance 105, and then measuring the temperature of the out-- going water as I do by means of the resistance 104, I am able to calculate the amount pif 'leat absorbed during the passage of the In the present case, all I care to know is the relative condition of the fire box with respect to its proper working temperature, and for this purpose the present pyrometer is admirably adapted. When the pyrometer is to be employed in measuring temperatures a suitable graduation of the same is necessary, -just as the ordinary mercury thermometer must be graduated.

The difference in temperature indicated by the difference in resistances 105 and 104 is a measure ofthe heat absorbed by the fluid flowing through the tube 111 from the medium whose temperature is to be measured. If the rate at which the fluid flows is maintained constant and the co-eflicient of absorption by the tube is practically constant the heat absorbed is directly proportional to the difference between the furnace temperature and the mean temperature of the fluid in the tube 111. Since the range of temperature dealt with in a case like this is not vsufficiently variable to seriouslyl affect the constancy of the co-eilicient of absorption, the fact that radiation is a function of the fourth power rather than the rst power is immaterial in our case.- Furthermore, since lthe mean temperature of the Huid in the pipe does not at any time vary more than a few degrees from afcertain mean lvalue close to that of room/temperature, the

effect of such variation when compared with the high temperature (between 1500o and 2500 F.) of 'the medium under consideration, would be ina. preciable.

It is apparent rom the above that the difference between resistances 105 and 104 is` for practical purposes a direct measure of the difference between the furnace temperature and room temperature. y

'Ihe Wheatstone bridge with the pyrometer and CO detector resistancesy is adapted to affect the relay 88 to cause a deflection of the galvanometcr invariably in one direction (which We will assume to be to the left as shown in the figure) whenever there is any C() in the products of combustion. The tendency of a drop in temperature is to cause a deflection of the galvanometer in the opposite direction (to the right in the ligure).

When the furnace temperature is at the predetermined value arms Gr and H are made equal by the insertion of resistance 90 which is in series with the resistance 105 exposed to the lower temperature.

The apparatus is designed so that Whenever CO (or other combustible gases) appear in the products of combustion they will when ignited in the combustion chamber of the CO detector create a greater'eifect upon t-he galvanometer than will the corresponding drop in temperature which is caused by the imperfect combustion.

In practice I set the value of the predetermined high efficiency temperature somewhat below the actually attainable maximum. The effect of this is to strengthen the tendency of the CO detector control to swing the galvanometer to the left (admitting more air). The result of this after final balancing is to admit a slight excess of air. This is done to insure absolute protection against insufliciency of air or imperfect combustion.

Since the motion of the galva-nometer pointer to the left as shown in the drawings invariably occurs upon the presence of CO in the products of combustion it therefore indicates imperfect combustion or lack of air and I may employ this relay or any standard galvanometer as an indicator of imperfect combustion. I can employ such galvanometer or other indicating instrument solelyas an indicator apart from any automatic control or in combination therewith.

In a similar manner, since the movement of the pointer to the right indicates a drop in temperature, I may employ the same galvanometer to indicate excess of air for such deflection.

In other Words, the relay, or galvanometer 88 may be used as a guide for manual control of the draft as well as an automatic control.

The damper control'bridge 89. thus takes .into account the temperature of the lire and the percentage of carbon-monoxide or other combustiblegases in the liuc4 gases and through the relay or galvanometer 88 the control afforded by these factors is exerted on the motor 87, the relay havingmovable contact 112 and the stationary contacts 113 and 114 for closing a circuit through either the reverse field 115 or through the forward field 116 to cause closing-or opening of the damper 17 as the case may be. The circuit for the motor 87 includes the common wire 117 and the forward field wire 118 and the reverse field wire 119. The closing of the circuit through either the forward or reverse field is controlled at two points, namely at the damper control relay 88 or at the stoker speed control relay 121.

The stoker speed control relay 121 is of the same general type as the steam meter relay 44, having a moving coil 123 provided with a swinging pointer or needle 122 bearing the blocks 124 and 125. The block 124 is adapted to swing under the plunger 126 or plunger 127 whereby the contacts 128 or 129 may' be closed to operate the motor 87 for the damper 17 over either the reverse field or the forward eld, respectively.

The block 125 is adapted to swing under either the plunger 131 or the plunger 132 for closing either the contacts 133 or the contacts 134, respectively, for a purpose to be later described. The plungers 126 and 127 in addition to the mechanical release which is afforded as illustrated in the relay 44 are provided each with an electrical release in the form of solenoids 136 and 137 connected. in series over the lines 138 and .139 with the common moving contact 112 of the damper controlled relay, which is connected over the wire 117 with the common return wire 117 for the motor 87.

The common return wire 117 is cut through the fuel bed condition relay contacts 141 Vover the wire 117b and 117c for a purpose to be described later.

The control exerted over the motor 87 and the damper 17 consists primarily of the carbon monoxide `detector for indicating the completeness of the combustion, the pyrometer for indicating temperature, the fuel bed condition relay for removing the control in case of unusual conditions relating to the fuel bed, and the stoker speed control circuit' which indirectly brings in control based upon boiler pressure, thickness of the fuel bed, quantity or rate of steam flow and speed of the stoker.

The purpose of the double control of the damper is first, to secure a prompt effect upon the air supply simultaneously with any change of the steam load and second to secure an accurate final adjustment of the air supply. causes unbalancing of the stoker speed control circuit which in turn promptly starts the control of the air supply through the damper thus securing a quick start. As soon as the first control becomes inaccurate as tested by the CO pyrometer combination,

the latter releases the damper controlmotor When the steam load varies it from any electrical connection with the stoker speed control relay, simultaneously causing the closing of a separate control circuit governing the same motor. The motion of the latter` will continue until the predetermined high efficiency temperature is reached when the motor will be automatically released by the damper control relay 88. The last feature evidently insures the most accurate adjustment of air supply which is practically possible.

In case thefuel bed conditions become noticeably wrong, it would be impossible to 'raise the temperature to the proper value no matter how the damper may be manipulated. For this reason, the damper control is automatically cut out until the proper fuel bed conditions are more nearly restored. l

rIhe fact that the fuel bed conditions are noticeably wrong may be indicated as by means of a lamp signal 181 or the like, at the desk of the executive ocer.

(3) Stoker speed control.

-eter 121 of the stoker speed control relay is bridged across from the common point of thearm-s I and J to the common point of the arms K and L. y v v The arm J contains the resistance 48 which is connected to the wires 144 and 145. This resistance 48 is varied in accordance lwith the steam meter rheostat, as it is a duplicate of resistance 42, which is calibrated in terms of B. `t.u. per unit of time.

The arm L contains the resistance 146 which is connectedthrough vthe wires 147 and 148. This resistance 146 is varied in accordance with the variationsl of steam pressure as indicated on the gage 149. The gage 149 may operate through a suitable relay such as indicated at 44 although I have shown the same as connected directly to the motor 151 for actuating the rheostat arm 152.

The arm K includes a resistance 153 which is varied in accordance with the vari-v ations of the gate 13 for controlling the thickness of fuel upon the traveling chain grate 7. This resistance 153 is connected in the arm K over the wires 154 and 155.

The gate 13 has an arm 156 which varies l resistance 153 for exerting `a control over the V`Wheatstone bridge 142. At the same time this arm 156 controls another resistance 157 in unison with the resistance 153 for a purpose later to be described.

The arm I of'the Wheatstone bridge 142 contains the balancing resistance 158 which is varied by means of the rotatable arm 159. The resistance 158 is connected-in the bridge 142 over the wires 161 and 162.

The relay 121 controls the operation of a motor 163 to cause the resistance 158 to be varied to balance the Vheatstone bridge 142. The manner in which this occurs is similar to the control exerted by the steam meter relay 44 over the corresponding motor 45. The motor 163 has a forward field 164 and a reverse eld 165 controlled over the wires 166 and 167, respectively. The wire 168 is a common return connected to the armature of the motor 163. Closing of the contact 133 controls a connection of the reverse field and the armature circuits and closing of the contacts 134 controls the connection of the forward field and the armature circuits.

lt will be noticed that the stoker speed control relay 121 not only controls the balancing resistance 158, butL also -another resistance 169 similar to it for a purpose later to be described, and the motor 163 at the same time controls the opening of valve 9 for governing the speed of the engine 8 which drives the travelingy chain grate 7.

rThe contacts 128 and 129 control the circuits of the damper control relay 87 as prev-iously explained and it is intended that during the operation of this system the stoker speed control circuit which-is directly responsive to the steam flow shall exert a control over the damper motor for a rough or approximate adjustment and that the carbon monoxide detector and the pyrometer shall exert the nal control over the damper so that the amount of air admitted shall be proportional to the amount of coal fed, but that the necessary correction for perfect combustion and proper temperature shall be made by an independent control. It is my purpose to control the speed of the stoker in direct proportion with the B. t. u. steam load per unit of time. This is accomplished as follows:

The steam load rheostat 48 has a resistance of value Rj which is; made directly propor- R12. n.. z Non i. e., in order that exactly the right amount 110 of fuel may be burned (by properly adjust- KiRi tional to the B. t. u. of steam load per unit 'of time, which is designated I; i. e.

where K5 is a constant.

The Stoker speed rheostat 158 xhas a resistance Ri which is made directly proportional to the stoker'speed s; i. e.

SIKiRi where Ki is a constant.

The fuel thickness rheostat 153 has a resistance of value Rk which is made to vary inversely in proportion to the fuel bed thickness, t; i. e.

(23) Heat input=ostH where c is a constant.

If the overall eliiciency of the system ,is N 70, the relation between heat outputor steam load I and the heat input, cstH is evidently NcstH 100 Substituting in the last Equation for I, s and t; from Equations 20, 21, and 22, respec tively, and utilizing the relation between .the resistance arms of the Wheatstone bridge 142 when its relay galvanometer 121 is at zero position, viz,

an (25) Rj R1 (26) RFRLRI 'we get,

Substituting for Rj from Equation (27) into Equation (26), we get,

Kk KiKk C Rk- Kj 100 NH-KNH B. t. u. per pound of fuel, H, and in overall efliciency, N

rllhis continuous recalibration is accomplished by motor 151 moving the arm 152 of the rheostat 146, the motor being actuated by the pressure gauge relay 149, which tends to maintain constant steam pressure in the steam header. Since constant pressure can not exist unlessthe steam load is exactly. taken care of, (the water 'level in the boiler being assumed to remain constant), relay 149 serves as the most accurate adjuster of stoker speed which is practically possible.

ple two similar boilers as here shown, the4 fact that the pressure in the main header will depend not upon any one boiler but upon the resultant effect of the two, must be taken into account. For example an extreme condition may be assumed when one boiler is practically idling .while the other is carrying the full load of the steam header. lf now the steam load rheostat 48 is calibrated so as to take care of exactly onehalf of the total steam load there is still the objection that the steam pressure will not reach its constant predetermined "alue until the rheostat 146 reaches such a value as to bring about the proper constant pressure and at the same time balance the Stoker speed circuit. For the particular case of one boiler idling and the other carrying the full load rheostat 146 would have to reach double its proper value in order to double the Stoker speed effect, so as to take careof the load. In order to distribute the load approximately equally between the two boilers, arm 152 of the pressure correction rheostat is made to move simultaneously over rheostats 146 and 270. Now the B. t. u. per pound of coal may for all practical purposes be assumed to be the same for both boilers and furthermore, the slight difference between the overall efficiencies of the two boilers will affect distribution of load only slightly. Therefore, it is apparent that by making the steam load rheostats of the stoker speed control` circuits of the two boilers equal to one-half the actual total steam load and by connecting rheostat 146 to the Stoker speed control of the first boiler and its duplicate 270 to the stoker speed control circuit of the second boiler, the load will be approximately equally divided. Thus if the fuel bed thickness is the same in the two boilers, the stoker speeds of the two boilers will be exactly the same, and if lit were not for any possible lvariations between the overall efiiciencies between the two boilers or between the fuel used in the two boilers the distribution in load between the two not the same the result is simply a difference between the Stoker speeds ofthe two boilers.

(4) Fuel bed condition indicator.

I shall now describe/the construction and operation of the fuel bed condition circuit and the control which it-exercises over the damper control circuit.

In order to maintain etiicient combustion Vit is necessary to maintain the drafts through the various parts of the boiler and lire in proper relation to each other.

The fuel bed condition circuit contains two Icontrolling elements the relation of which indicates the condition of the fuel bed. When the latter becomes noticeably wrong, the galvanometer of this circuit stops the automatic regulation of the draft.

If the condition of the fuel bed is correct,

the ratio between the indication of the two draft gauges is constant for a given boiler setting and for a given fuel. After once setting the calibration rheostat for a proper draft gauge ratio any irregularities in the fuel 'bed will cause a deflection of the galvanonleter 175. The factors which affect this fuel bed condition circuit are as follows:

1. Drop in pressure across the fuel'bed.

2. Drop in pressure across the baiiies and tubes.

3. The fuelbed calibration rheostat.

The fuel bed condition circuit comprises the lVheatstone bridge 171 having the arms M, N, O and P. The battery circuit 172 is bridged from the common point of arms M-O to the common point of the arms N-P and the relay or galvanometer circuit 172-178 is bridged across from the common point of arms M-N to the comon point of the arms O-P. The galvanometer 175 is of the type employed in the relay 44 previously described, and has a pointer or needle 176 bearing the block 177 which is adapted to swing under the plungers 178 or 17 8 when the bridge is out of balance whereby the contacts 141 or 141 are opened disabling the damper control regulating apparatus and closing the contacts 179 or 179 thereby lighting the signal lamp 181 or 181 vas the case may be which may be located in the chief engineers oiiice or any other available place for indicating that the normal condition of the fuel bed or of the baffles or arches does not prevail and that immediate attention is required.

The arm M of the 'Vheatstone bridge 171 contains a resistance 182 which has taps 183 projecting into the horizontal arm 184 of the draft gage 185. This draft gage comprises a U-cliaped tube with the horizontal portion 184, mercury being kept in the lower portion 186 of this tube and extending into the horizontal arm for short circuiting to a greater or less extent the resistance 182 according to the differences of pressure prevailing at the openings 187 and 188. rfhe opening 187 is located below the fuel bed on the atmosphere side of the same. The opening 188 is located above the fuel bed and communicates with the right-hand side of the U-tube 186. The resistance of the rheostat 182 is varied directly with the draft by removing the short circuiting effect of the mercury column which is moved by the difference in pressure on the two sides of the U-tube 186. A similar draft gage 189 communicates by way of the pipe 191 with the opening 188 above the fire bed and by means of the pipe 192 with another opening 193 placed adjacent the outlet for the exhaust gases. The resistance 194 is connected by the wires 195 and 196 in the arm N of the Wheatstone bridge 171 comprising the fuel bed condition circuit. rlhe resistance 182 is connected in the arm M by Way of the wires 197 and 198. The resistance of the rheostat 194; is also varied with the draft by means of the difference in pressure acting upon the two legs of the U-tube 186 and moving the column of mercury to vary the short circuiting effect upon the resistance 194.

The arm P has a rheostat 199 containing an adjustable resistance which is adapted to be set at a certain value to correspond to the characteristics of the furnace or the characteristics of the fuel bed. l term this rheostat the fuel bed calibration rheostat.

The arm O of the bridge 171 contains a I fixed resistance 201.

The operation of this fuel bed condition circuit is as follows. The draft gage 185 which controls the resistance 182 is governed by the drop in pressure across the fuel bed. I'lhe draft gage 189 which is controlled by the drop in pressure through the baflies and arches controls the resistance 194. lf the absolute -value of the draft varies, this does not affect the relative values so long as other conditions remain equal, but if the conditions change either across the fuel bed or across the tubes, arches and baffles, the bridge 171 is thrown out of balance. Under extreme conditions it would naturally be inadvisable to have the pyrometer and carbon vmonoxide detector attempt to make regulation f the air supply since no true relation between the air and the fuel would at such a time exist. Consequently, the proper thing to do is 'to cut off such automatic controls and notify some supervisoryoiiicer of the fact that conditions exist which make the automatic regulation impossible. The galvanometer relay 175 performs this function in opening the circuit of the damper control motor 87 at the contacts 141er 1111 and closing the contact of the signal device. 181 or 181 advising the chief engineer or. some other supervisory officer of abnormal conditions in the particular boiler.

The direction ofdeection will determine which one of the signal lamps will be lighted but the 'deflection in either direction (if more than a predetermined minimum) will open the damper control circuit.

(5) Feed water control.

l shall next describe the automatic feed water control.

rlhe feed water control is governed by the following factors which l shall explain more in detail, namely:

1. The steam flow from the boiler.

2. The pressure prevailing on the boiler.V

The latter control may be omitted.

The above factors are modified or limited by certain corrections which comprise the following: i

1. Nater level prevailing in the boiler.

2.- rlhe How of feed water from the feed pump.

As I have previously explained, in order to maintain a constant level within the boiler, it is essential that as much water be injected into the boiler as leaves the boiler in the form of steam. Consequently, if there are no leaks, thev flow of steam from the boiler is an accurate measure o'f the water to be injected into the boiler. However, there is the matter of leakage and inaccuracy of the instruments to be taken into account and to this end it is advisable that 4some check or safeguard be put on conditions. Due to a small Variationin calibration be tween the steam meter and the water How meter it would be possible for a cumulative variation either to run the boiler dry or to flood the same unless some means were provided to guard against such cumulative action or error. To this end, I use the balance between steam ow and water ow as arough or working relation and make the final or accurate adjustment of this relation or proportion subject to the water level in the boiler.-

The feed water control circuit comprises the Wheatstone bridge 202 having the arms Q, R, S and T. rll`he battery circuit 203 is connected across the bridge from the common point of the arms Q and S to the common point of the arms R and T, while the circuit of the galvanometer or relay 204 is connected across the bridge from the common point of the arms Q and R to the Ycommon point of the arms S and T. The galvanometer relay 204 which is the water feed control relay has a moving contact 205 connected to the common return Wire 206 andthe two cooperating stationary contacts 207 and 208 which are connected to the wires `209 and 210 leading respectively to the forother suitable means.

ward and to the reverse field ofthe feed. Water control motors.

As I have previously explained the feed water pipe 21 contains a control valve 23 which may be governed by the feed water control motor 211 having the forward field 212 and thev reversed field 213. The pump 22 which supplies feed water to the boiler is shown in this case as a steam pump having a throttle valve 214 which is adapted to be governed b the control motor 215 havlng the forward eld 216 and the reverse field A two-way switch 218 is connected to the leads 206, 209 and 210 leading to the feed water control relay and this switch may be connected to the leads 219, 220 and 221 of the valve control motor 211 or to the leads of the motor 215 which controls the throttle valve 214 for the steam pump.

The arm Q, of the bridge 202 contains a resistance 222 which is adapted to be affected by the steam flow in the same manner as the resistance 28 in the steam meter body 25. This resistance is connected over leads 223 and 224 to the arm Q.

The arm R contains the feed water meter resistance 225 which is connected in series by means of the leads 226 and 227. The resistance 225 is enclosed in one leg of a generally U-shaped meter tube which is subjected to diferences in pressure by the flow of feed water through they pipe 21 as by means of the Pitot tubes 228 and 229 or The arrangement is such that the resistance 225 is directly proportional to the flow of feed water through the pipe 21.-

The arm T of the bridge 202 has a resistance 230 connected therein in series by means of the leads 231 and`232.

The arm S comprises two resistances placed in series, namely, the resistance 233 and resistance 234. It is desirable that the resistance of this arm be made lesss than a certain specified amount if the water level drops and be made greater than a certain specified amount if the water level rises beyoud a predetermined amount. To this end,

have provided the resistances 235 and 236 which are adapted to be placedl in shunt with the resistances 233 and 234 respectively, by means of the mercury column contained in the bottomof the U-tube 237 which is a gage for securing a water level correction of the feed water supplied to the boiler. The U-tube 237 has a horizontal portion 238 in which three contacts are placed, namely, the central contact 240, the high level contact 241 and the low level contact 242. The horizontal arm 238 is connected by a pipe 243 with the bottom portion of the steam and water drum 2 of the boiler 1. The other leg of the U- tube 237 is connected to a vertical pipe 244 which extends within the interior of the conduit 245, this conduit being connected to the steam space of the steam and water drum 2. The upper end of the conduit 245 into which the Vertical tube 244 projects, lies above the level of the water in the drum 2 so that steam which condenses into said conduit will run back into the steam and water druln except such steam and water as is trapped in the open mouth of the tube 244. A

The central contact 240 is connected by means of the wire 246 to the point joining the resistances 233 and 234. The low level contact- 242 is connected by means of the wire 247 with one end of the resistance 236, the other end of said resistance being connected in shunt of a part of all of the resistance 234. The high level contact 241 is connected by way of the wire 248 to one end of the resistance 235, the other end of said resistance being connected in shunt across part or all of the resistance 233. It can now be seen that as the water level rises, the pressure on the.righthand side of the U-tube 237 will increase and will finally cause the .conf tact 242 to break with vthe mercury in the U-tube with the result that the circuit between Wires 246 and 248 is broken, whereby the resistance of the arm S is increased and in fact is caused to rise to its highest value because both shunts are open. The effect of this resistance upon the bridge will be to reduce or stop the iow of water by closingl either the steam control throttle valve 214 or by closing the water control Valve 23 depending upon which one is in operation for control. When the water level drops sufliciently again to be substantially normal, the mercury will close contact between the two contacts 240 and 241 whereupon the shunt resistance 235 is closed about all or a portion of the resistance 233. This is the normal condition of operation. If, now, the level should drop below a predetermined amount, contact will be made between contact 240 and contact 242 whereupon the shunt resistance 236 'will be closed reducing the resistance of the arm S and causing a corresponding change upon the Wheatstone bridge 202 to cause an increased rate of Water delivery to the boiler. As soon as the 'normal "level has been restored the shunt resistance 236 will be opened whereupon conditions will be restored to normal. l

This feature of water leve'. control may -operate directly upon the feed water injec tion apparatus without any comparison of steam flow and water flow.

I shall now describe the construction and operation of the efficiency meter which in dicates the overall efficiency of the plant.

(6) E /vz'efncy meter.

The purpose of the etliciency meter is to ion determine the ratio of the heat output to the heat input.

1. Fuel bed thickness.

2. Stoker speed.

3. Fuel B. t. u.

4j Steam flow:

The first three factors are employed to compute the B. t. u. input and the fourth factor is employed in computing the B. t. u.

output of the plant, and since efficiency is a ratio of output to input, it can be seen that the matter of securing this ratio is in my system relatively simple. For this purpose, T employ a circuit comprising a Wheatstone bridge 250 having the arms U, V. W and X. The battery circuit 251 is connected from the common point between the arms U and W to the common point between the arms V and X. The galvanometer circuit 252 is connected from the common point between the arms U and V to the common point between the arms W and X.

The relay 253 which is connected -in the galvanometer circuit is preferably of the type shown in connection with the steam meter at relay 44 although a polarized contact making relay may be employed as indicated. This relay controls the circuit of an electric motor 254 which in turn operates the shaft of an indicator 255 having an indicator arm 256 which serves both as an indicator for overall eliiciency'and also serves as a contact making arm for varying a balancing resistance 257 connected in series in the arm Uv of the Wheatstone bridge 250.

The arm W has a resistanceconnected in series, namely, the resistance 48 on the steam meter rheostat 43, this resistance being connected by means of the wires 258 and 259.

The arms V'and C have xed resistances connectedA therein, these resistances being fixed in, the sense that they are adjusted to bring about the proper constants of the circuit and are thereafter not varied.

The arm U which is to take into account the factors-of B. t. u. of thefuel, the thickness of the 'fuel bed, the rate at which it is fed and eiiiciency contains in series the resistances 260, 169, 157 and 257 respectively. The resistance 260 is mounted .on the fuel B. t. u. rheostat 261, the value of the resistance 260 being controlled by means of an adjustable arm `262 which is set according to a. calorimeter testof the fuel. This rheostat yisv graduated in termsof a. function of B. t. u. per pound of coal,` so that the engineer in charge may make a test of the fuel and set the rheostat accordingly. This re- Sistance 260 is connected in series in the arm U by meansof thewires 263i and 264.

- The resistance 169 whichas previously eX.- plained 'is varied in, accordance with the feed of the vStoker' isconnected in series in the arm U` by means of the wires 265c and.

neaaeao Heat inputzcstH (see 23) Heat outputzl.

where, s is the stoker speed, t is the fuel bed thickness, H is the B. t. u. per pound of fuel a and l is the B. t. u. of steam loa/d per unit of time, while c is a constant.

Since overall el'iciency is the ratio of heat output to heat input, we have Heat output l (29) N%100 Heat input c QH ln the last equation there are tive factors to be compared. Therefore, considering the fact that a l/Vheatstone bridge contains only four arms each of which may be made to take care of only ,one variable V( for multiplying and dividing purposes), it was necessary for me to devise a novel form of calibrating the resistances corresponding to the factors they measure in order that it may be possible to take account of as many' factors as may be required by means of only one Wheatstone bridge.

Thus, instead of making the resistances 260, 169, 157, 47, 257 directly proportional to the quantities, H, s, t, I, and N I make them proportional to the logs (natural or otherwise) of the same quantities; i. e. I make,

I then connect the resistances R260, Rm. Rm, and Rg, in the common arm U of the efficiency Wheatstone bridge circuit, and the resistance R4, in arm W of the same bridge. Arms V and X are made equal. Therefore, when the relay galvanometer 253 reads zero, itis evident that Substituting into Equation (37) from 30, 31, 32, 33, 34, we get,

(38) K8 log H+K log s-i-K, log H-K, log N=K log I Thus, when the eciency Wheatstone bridge is balanced, rheostat 257 is a measurement of overall efficiency, and the condition R2,=Ke log N (see 35) is satisfied. Evidently, the scale of Athis rheostat may be made to read overall eiliciency directly.

I believe that the operation of the system will be clear from the above description, but I shall a ain review/briefiy the overall re-4 lations o the system. The steam meter is the heart of the whole system since it is a primary factor from' which all the others are regulated either in a primary sense or in a secondary sense.

First, considering that we have steam iiow of a character which varies with the load but which is to occur at constant pressure, it is my aim to provide suiicient fuel, air and water which when combined properly will produce steam at the rate at which it is drawn off and will maintain the boiler at the proper pressure. To-this end, I control the stoker speed .directly from the steam meter rheostat as a primary source of regulation of the fuel input to the furnace of the boiler. At the same time, however, I must not permit the pressure to drop below a predetermined value hence the stoker speed has a secondary speed control in the form of a variable calibration rheostat which varies according to pressure. Furthermore, the amount of fuel which is burned in the fire depends upon the thickness of the fuel bed in addition to the speed of the stoker, consequently, I take this into account in computing the rate at which the stoker is run.

The control of the draft, that is, the air which flows to consume the fuel and produce heat, is primarily made dependent upon the steam load and the Stoker speed regulation or perha s I should state more exactly that it is ma e to depend upon the amount of coal fed per unit of time. This is a rimary or rough approximation of reguatio'n of the air supply, the finer adjustments being made to balance the amount of air vrequired accurately to the amount of coal fed so that an intense combustion of proper temperature will be carried on and a combustion which is complete in not leaving y ,any carbon monoxide or other combustible product. These two controls, namely, the intensity control and the completeness control, I effect throughthe pyrometer and the carbon monoxide detector devices which I have heretofore described.

The control of the Water fed to the boiler depends directly upon the rate of steam flowing from the boiler, but since errorsv in the estimate even 'of a very minute character may tend under continued operation to give accumulative error which Wouldeither flood the boiler or cause it to run dry, I provide certain checks.

These checks comprise a water level check for giving a. secondary or minor control of the wat-e1' iiow from the water level, this check really forming a sort of recalibration (f the ratio between steam flow and water ow. v

In addition, the pressure control is employed to hold off any sudden increase in feed water from a sudden drop in steam pressure. This control may be dispensed with as previously indicated, but I find that it assists in a smoother operation of the system.

The above three features, namely, the control of the fuel, control of the air and con-., trol ofthe water are the fundamental con` trols which my system employs. However, these controls are subject in general to the condition of the fuel bed which is safeguarded by an indicator or other instrument responsive to the condition of the re and furnace,-this condition being ascertained by means of draft gages as above explained.

It will be appreciated that I do not intend to limit the control strictly to the firing of coal or other solid fuels, as it is obvious that the same .principles control the feeding of liquid or gas lires.

The efficiency meter is possible because all of the elements for the same are present and it is merelyv a question of combining the ele# ments properly to give an overall indication of efficiency.

I claim:

1. In combination, a boiler having a furnace, a meter measuring the heat in the steam delivered from the boiler, automatic fuel feeding means for feeding fuel to the boiler, connections between said meter and feeding means controlled by said meter for varying in part the actionl of said feeding lil means, an air supply device, connections for varying in part the air supply as a function of fuel feed, and means controlled by the condition of the furnace for varying in part the air Supply.

2. In combination, a boiler having a meter for measuring the B. t. u. delivered thereby, a furnace for the boiler, means for Supplying fuel to the furnace as a function in part of the. rate of heat delivery, automatic means controlled in part in accordance with the rate of fuel feed for governing the air supplied to the furnace and means for adjusting the Same, said adjusting means being governed in part by the temperature of the fire box.

3. ln combinat-ion, a boiler having a meter for measuring the heat delivered from the boiler, a furnace, automatic means for feeding fuel to the furnace as a function in part of the heat flow from the boiler, a draft control device. control means responsive in part to completeness of combustion in the furnace, control means responsive in art to the rate of fuel flow, and connections between Said device and both said control means.

ll. ln combination, a boiler, a heat How meter, an automatic Stoker controlled in part by the heat How meter, an automatic damper regulator controlled primarily by the Stoker speed, a carbon monoxide detector for measuring the completeness of combustion, said automatic damper regulator being controlled Secondarily by said carbon monoxide de tector.

l5. lin combination, a boiler, a heat lovv meter, a furnace, a. fuel Stoker, a draft regulator, pyrometer means for measuring the furnace temperature, and control connectiens from the meter to the Stoker, and from both Stoker and pyrometer. means to the draft regulator'.

6. lin combination, a boiler having a furnace, means for automatically feeding fuel to the furnace, an automatic draft regulator controlled in p'art by the feeding means, a carbon monoxide detector, and an automatic means controlled by the carbon monoxide detector for partially controlling said draft control device.

7. lln combination, a furnace, an automatic fuel feed device therefor, an automatic draft control device partially governed thereby, pyrometer means for measuring the temperature of combustion in the furnace, and contro connections therefrom to said draft contro 8. ln combination, a steam boilerhaving a furnace, a meter for measuring the heat from said boiler, means controlled by Said meter for automatically varying in part the Leaaeee fuel supply, and additional means controlled by the pressure of the steam in the boiler for varying in part the action of said fuel feeding means.

9. In combination, a boiler having a furnace, a meter for measuring the heat flow from the boiler, a mechanical Stoker comprising a traveling surface, means governed by said steam flow meter for varying in'part the speed of said traveling surface, and means controlled by the thickness of `fuel bed on said traveling surface for varying in part the speed of the same.

l0. ln combination, a boiler havin a furnace, n said furnace having a mec anical Stoker, a meter for the boiler for measuring the heat delivered thereby, an electric circuit governing the speed of the Stoker, Said circuit comprising a resistance controlled by said meter, a resistance controlled by pressure in the boiler, and a relay governed by said circuit for controlling the speed of said Stoker. l

l1. ln combination, a boiler havin a furnace, Said furnace having a mec anical Stoker, a meter for measuring the heat flowing ,from the boiler to the load, a lheat- Stone bridge comprising a resistance varied in part in accordance vvith the heat flow, a resistance varied in ypart in accordance with the pressure in the boiler and a resistance l' varied in part in accordance with the thickness of 'fuel on the mechanical Stoker, a resistance vcontrolled in part by the Stoker speed, and a relay, Said rela controlling the speed of the mechanical Sto er and controlling the variation of said resistance corresponding to the Stoker speed for balancing said lVheatStone bridge.

12. ln con'ibination, a furnace having a traveling grate for burning fuel, means for i controlling the discharge of fuel upon said i grate, means for controlling the rate ofadvance of said grate, Said latter means being controlled by the fuel discharging means to control the rate at which fuel is burned in the furnace.

13. ln combination, a boiler havin a furnace, said furnace having a mec anical Stoker, a meter for measuring the heat delivered by the boiler to the load, -means for maintaining the Stokery Speed proportional to the steam load, and interpolated means for recalibration of the constant of proportionality between load and Stoker speed to correct for variation in fuel bed thickness, B. t. u. per pound of yfuel overall efficiency of the furnace, and for errors in. the steam meter.

ln yWitness whereof, l hereunto subscribe my name this 25th day of Se tember, 1920.

JULU NAlMAN.. 

